Absorbent articles comprising low basis weight films exhibiting low glue burn through

ABSTRACT

Low basis weight films having a heat capacity×density value of greater than about 970,000 Ws/m 3 K, as measured by the method described herein, the films having a basis weight of less than about 16 gsm and comprising at least about 10% polypropylene.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/133,404filed on Jun. 5, 2008, which claims the benefit of U.S. ProvisionalApplication No. 60/933,205, filed on Jun. 5, 2007.

FIELD OF THE INVENTION

The present invention relates to absorbent articles comprising low basisweight films exhibiting low glue burn through. Specifically, the lowbasis weight films of the present invention include polypropylene tohelp achieve low glue burn through, as determined by the methoddescribed herein.

BACKGROUND OF THE INVENTION

Low film basis weights may increase a film's thermal sensitivity to hotmelt systems. As a result, the risk of hot melt adhesives burningthrough the film increases. Glue burn through (GBT) occurs when the hotglue partially or completely melts the polymeric film in an area so thatthe thickness of the polymer is reduced or no longer exists. Glue burnthrough can occur by two different mechanisms: instantaneous melting ormechanical pressure. Instantaneous melting occurs when the film meltsinstantaneously when the hot adhesive contacts the web, usuallyresulting in contamination severe enough to tear the film web. When glueburn through occurs from the mechanical pressure mechanism, the glue andfilm are in contact and the area goes under a mechanical nip. Themechanical nip applies pressure to the area where the soft film porescollapse or forces the glue through the film. Glue burn through canpotentially impact the product by eliminating or weakening the filmstructure or altering the opaqueness of the film. Thus, the film isdiminished in performance (may cause leakage from pinholes or thermalmelting), integrity (could tear easily), and appearance (looksplastic/cheap or consumer perceives it as product failure).

Higher basis weight films typically do not exhibit glue burn through.However, higher basis weight films are more expensive than lower basisweight films. Conversely, lower basis weight films are less expensivethan higher basis weight films, but many lower basis weight filmsexhibit glue burn through. Thus, a need exists for a lower basis weightfilm that exhibit lower glue burn through.

SUMMARY OF THE INVENTION

The present invention provides for a low basis weight film that does notexhibit glue burn through. The low basis weight films of the presentinvention have a heat capacity×density value of greater than about970,000 Ws/m³K, as measured by the method described herein. The films ofthe present invention have a basis weight of less than about 16 gsm, andthe film comprises a polymeric resin that comprises at least about 10%polypropylene. The low basis weight films of the present invention maybe used in absorbent articles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an article made according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the following terms have the following meanings:

As used herein, the term “absorbent articles” refers to devices thatabsorb and contain body exudates, and, more specifically, refers todevices that are placed against or in proximity to the body of thewearer to absorb and contain the various exudates discharged from thebody. Absorbent articles may include diapers, training pants, adultincontinence undergarments, feminine hygiene products, breast pads, caremats, bibs, wound dressing products, and the like. As used herein, theterm “body fluids” or “body exudates” includes, but is not limited to,urine, blood, vaginal discharges, breast milk, sweat and fecal matter.

As used herein, the term “absorbent core” refers to the component of theabsorbent article that is primarily responsible for fluid handlingproperties of the article, including acquiring, transporting,distributing and storing body fluids. As such, the absorbent coretypically does not include the topsheet, backsheet or outer cover of theabsorbent article.

As used herein, the term “bonded” refers to different materials beingattached (cohesively or adhesively) in at least a portion thereof. Theattached portions may be random or may have a pattern such as stripes,spirals, dots, and the like. The attached portions may be located at theperipheries, throughout the surface area, or both. Suitable attachmentmeans known in the art may be used, including but not limited toadhesives, heat, pressure, crimping, ultrasonic, chemical (via hydrogenbonds or other cohesive forces), mechanical (e.g., fasteners,entanglements), hydraulic, vacuum and combinations thereof.

As used herein, the term “diaper” refers to an absorbent articlegenerally worn by infants and incontinent persons about the lower torsoso as to encircle the waist and legs of the wearer and that isspecifically adapted to receive and contain urinary and fecal waste. Asused herein, term “diaper” also includes “pants” which is defined below.

As used herein, the term “disposable” is used in its ordinary sense tomean an article that is disposed or discarded after a limited number ofusage events over varying lengths of time, preferably less than about 20events, more preferably less than about 10 events, even more preferablyless than about 5 events, and most preferably less than about 2 events.

As used herein, the term “joined” encompasses configurations wherein anelement is directly secured to the other element by affixing the elementdirectly to the other element, and configurations wherein the element isindirectly secured to the other element by affixing the element tointermediate member(s), which in turn are affixed to the other element.

The term “longitudinal” refers to a direction running from a waist edgeto an opposing waist edge of the article and generally parallel to themaximum linear dimension of the article. Directions within ±45° of thelongitudinal direction are considered to be “longitudinal”.

The term “lateral” refers to a direction running from a side edge to anopposing side edge of the article and generally at a right angle to thelongitudinal direction and in the same plane as the longitudinaldirection. Directions within ±45° of the lateral direction areconsidered to be “lateral”.

As used herein, the term “nonwoven” refers to a web that has a structureof individual fibers which are interlaid forming a matrix, but not in anidentifiable repeating manner. Nonwoven webs may be formed by a varietyof processes known to those skilled in the art, for example,meltblowing, spunbonding, wet-laying, air-laying, and variousbonding-carding processes.

The terms “pant” or “training pant”, as used herein, refer to disposablegarments having a waist opening and leg openings designed for infant oradult wearers. A pant may be placed in position on the wearer byinserting the wearer's legs into the leg openings and sliding the pantinto position about a wearer's lower torso. A pant may be preformed byany suitable technique including, but not limited to, joining togetherportions of the article using refastenable and/or non-refastenable bonds(e.g., seam, weld, adhesive, cohesive bond, fastener, etc.). A pant maybe preformed anywhere along the circumference of the article (e.g., sidefastened, front waist fastened). While the terms “pant” or “pants” areused herein, pants are also commonly referred to as “closed diapers”,“prefastened diapers”, “pull-on diapers”, “training pants” and“diaper-pants”. Suitable pants are disclosed in U.S. Pat. No. 5,246,433,issued to Hasse, et al. on Sep. 21, 1993; U.S. Pat. No. 5,569,234,issued to Buell et al. on Oct. 29, 1996; U.S. Pat. No. 6,120,487, issuedto Ashton on Sep. 19, 2000; U.S. Pat. No. 6,120,489, issued to Johnsonet al. on Sep. 19, 2000; U.S. Pat. No. 4,940,464, issued to Van Gompelet al. on Jul. 10, 1990; U.S. Pat. No. 5,092,861, issued to Nomura etal. on Mar. 3, 1992; U.S. Patent Publication No. 2003/0233082 A1,entitled “Highly Flexible And Low Deformation Fastening Device”, filedon Jun. 13, 2002; U.S. Pat. No. 5,897,545, issued to Kline et al. onApr. 27, 1999; U.S. Pat. No. 5,957,908, issued to Kline et al on Sep.28, 1999.

As used herein, the term “region” refers to a zone or an area comprisinga material being physically, chemically, or visually distinguishablefrom surrounding or adjoining materials. Various regions of materialsmay include transitional regions in between. The regions may bepositioned in the z-dimension or in the xy-dimension. As used herein,the term “z-dimension” refers to the dimension orthogonal to the lengthand width of the structure or article. The z-dimension usuallycorresponds to the thickness of the structure or article. As usedherein, the term “xy-dimension” refers to the plane orthogonal to thethickness of the member, core or article when the member, core orarticle is in a flat-out state. The xy-dimension usually corresponds tothe length and width, respectively, of the structure or article in aflat-out state.

Absorbent Articles

FIG. 1 depicts the absorbent articles of the present invention, e.g.,diaper(s) 20, which comprise a liquid pervious topsheet 10, a backsheet12 that is at least partially joined to the topsheet 10, an absorbentcore 18 disposed at least partially between the topsheet 10 and thebacksheet 12, a first cuff 16 along a longitudinal edge 22 of thetopsheet 10. In certain embodiments, the absorbent articles mayadditionally include one or more components selected from the groupconsisting of an outer cover, side panels, an elastic feature, afastening system, and combinations thereof.

An outer cover (which may comprise the backsheet) forms the chassis,onto which other components of the diaper are added to form the unitarystructure of the diaper. In alternative embodiments, the article may bepreformed by the manufacturer to create a pant. The term “pant”, as usedherein, refers to disposable garments having a waist opening and legopenings designed for infant or adult wearers. A pant may be placed inposition on the wearer by inserting the wearer's legs into the legopenings and sliding the pant into position about the wearer's lowertorso. A pant may be preformed by any suitable technique including, butnot limited to, joining together portions of the article usingrefastenable and/or non-refastenable bonds (e.g., seam, weld, adhesive,cohesive bond, fastener, etc.). While the term “pant” is used herein,pants are also commonly referred to as “closed diapers”, “prefasteneddiapers”, “pull-on diapers”, “training pants” and “diaper-pants”.Suitable pants are disclosed in U.S. Pat. Nos. 5,246,433; 5,569,234,6,120,487, 6,120,489, 4,940,464, 5,092,861, 5,897,545, 5,957,908, andU.S. Patent Publication 2003/0233082A1.

The absorbent articles of the present invention comprise a topsheet 10.The topsheet is preferably compliant, soft feeling, and non-irritatingto the wearer's skin. It can be elastically stretchable in one or twodirections. The topsheet has at least one longitudinal edge 22 and inmost instances has two. Further, the topsheet is liquid pervious,permitting liquids (e.g., menses, urine, and/or runny feces) to readilypenetrate through its thickness. A suitable topsheet can be manufacturedfrom a wide range of materials such as woven and nonwoven materials;apertured or hydroformed thermoplastic films; porous foams; reticulatedfoams; reticulated thermoplastic films; and thermoplastic scrims.Suitable woven and nonwoven materials may comprise of natural fiberssuch as wood or cotton fibers; synthetic fibers such as polyester,polypropylene, or polyethylene fibers; or combinations thereof. If thetopsheet includes fibers, the fibers may be spunbond, carded, wet-laid,meltblown, hydroentangled, or otherwise processed as is known in theart. One suitable topsheet comprising a web of staple-lengthpolypropylene fibers is manufactured by Veratec, Inc., a Division ofInternational Paper Company, of Walpole, Mass. under the designationP-8.

Preferred topsheet for use in the present invention are selected fromhigh loft nonwoven topsheets and apertured film topsheet. Apertured filmtopsheet typically are pervious to bodily exudates, yet non-absorbent,and have a reduced tendency to allow fluids to pass back through andrewet the wearer's skin. Suitable apertured films include thosedescribed in U.S. Pat. Nos. 5,628,097, 5,916,661, 6,545,197, 6,107,539,and PCT Patent Publication WO 00/69382 A2.

Further, suitable topsheet materials for depositing solid excretionsthereon may include nonwovens having apertures, which are at least inthe portions that are aligned with the feces deposition region of thearticle. Suitable apertured nonwovens are described in more detail inU.S. Pat. Nos. 6,414,215, 5,342,338, and 5,941,864 and U.S. PatentPublication 2002/017376. In another embodiment of feces handlingarticles, such topsheets can be combined with feces handling members,e.g., underlying such topsheets, and which are further described in theabovementioned patent documents.

Suitable formed film topsheets are described in U.S. Pat. Nos.3,929,135, 4,324,246, 4,342,314, 4,463,045, 5,006,394. Other suitabletopsheets may be made in accordance with U.S. Pat. Nos. 4,609,518 and4,629,643. Such formed films are available from The Procter & GambleCompany of Cincinnati, Ohio as “DRI-WEAVE” and from TredegarCorporation, based in Richmond, Va., as “CLIFF-T.”

Preferably, at least a portion of the topsheet is made of a hydrophobicmaterial or is treated to be hydrophobic in order to isolate thewearer's skin from liquids contained in the absorbent core. If thetopsheet is made of a hydrophobic material, preferably at least aportion of the upper surface of the topsheet is treated to behydrophilic so that liquids will transfer through the topsheet morerapidly. The topsheet can be rendered hydrophilic by treating it with asurfactant or by incorporating a surfactant into the topsheet. Suitablemethods for treating the topsheet with a surfactant include spraying thetopsheet material with the surfactant and/or immersing the material intothe surfactant. A more detailed discussion of such a treatment andhydrophilicity is contained in U.S. Pat. Nos. 4,988,344, 4,988,345, and4,950,254. A more detailed discussion of some suitable methods forincorporating a surfactant in the topsheet 24 can be found in U.S.Statutory Invention Registration No. H1670. Alternatively, the topsheetmay include an apertured web or film which is hydrophobic. This may beaccomplished by eliminating the hydrophilizing treatment step from theproduction process and/or applying a hydrophobic treatment to thetopsheet, such as a polytetraflouroethylene compound like SCOTCHGUARD ora hydrophobic lotion composition, as described below. In suchembodiments, it is preferred that the apertures be large enough to allowthe penetration of aqueous fluids like urine without significantresistance.

Any portion of the topsheet may be coated with a lotion as is known inthe art. Examples of suitable lotions include those described in U.S.Pat. Nos. 5,607,760, 5,609,587, 5,635,191, 5,643,588, and 5,9680,25. Thelotion may function alone or in combination with another agent as thehydrophobizing treatment described above. The topsheet may also includeor be treated with antibacterial agents, some examples of which aredisclosed in PCT Publication No. WO 95/24173. Further, the topsheet, theouter cover or any portion of the topsheet or outer cover may beembossed and/or matte finished to provide a more cloth like appearance.

The topsheet may comprise one or more apertures to ease penetration ofexudates therethrough, such as urine and/or feces (solid, semi-solid, orliquid). The size of at least the primary aperture is important inachieving the desired waste encapsulation performance. If the primaryaperture is too small, the waste may not pass through the aperture,either due to poor alignment of the waste source and the aperturelocation or due to fecal masses having a diameter greater than theaperture. If the aperture is too large, the area of skin that may becontaminated by “rewet” (from the article) is increased. Typically, theaperture should have an area of between about 10 cm² and about 50 cm².The aperture preferably has an area of between about 15 cm² and 35 cm².

Further, the topsheet may be fully or partially elasticated or may beforeshortened so as to provide a void space between the topsheet and thecore. Exemplary structures including elasticized or foreshortenedtopsheets are described in more detail in U.S. Pat. Nos. 4,892,536,4,990,147, 5,037,416, and 5,269,775.

The absorbent article further comprises a first cuff 16 along alongitudinal edge 22 of the topsheet 10. This first cuff 16 is usefulfor providing improved containment of liquids and other body exudates.First cuffs 16 may also be referred to as outer leg cuff, leg bands,side flaps, leg cuffs or elasticized cuffs. U.S. Pat. No. 3,860,003describes a disposable diaper which provides a contractible leg openinghaving a side flap and one or more elastic members to provide anelasticized leg cuff.

The first cuff 16 may be constructed in a number of differentconfigurations, including those described in U.S. Pat. Nos. 3,860,003,4,636,207, 4,695,278, 4,704,115, 4,795,454, 4,900,317, 4,909,803(Reissued as USRE34920), 5,085,654, 5,492,751, 6,476,288 and SIR H1630.

Additionally, an absorbent article of the present invention may includeone or more second cuffs that also provide improved containment ofliquids and other body exudates. Second cuffs may also be referred to asbarrier leg cuffs, inner leg cuffs or “stand-up” elasticized flaps. U.S.Pat. Nos. 4,808,178 and 4,909,803 (Reissued as USRE34920) describedisposable diapers having “stand-up” elasticized flaps that improve thecontainment of the leg regions.

First cuff and second cuff may both be provided by way of a dual cuff,as exampled in U.S. Pat. Nos. 4,695,278 and 4,795,454. Additional cuffsmay be provided in an article of the present invention as detailed in USStatutory Invention Registration H1630.

The backsheet 12 may or may not be impervious to fluids (e.g., menses,urine, and/or runny feces). Accordingly, one embodiment of the backsheetis manufactured from a thin plastic film, although other flexible liquidimpervious or pervious materials may also be used. As used herein, theterm “flexible” refers to materials which are compliant and will readilyconform to the general shape and contours of the human body. Thebacksheet 12 prevents the exudates absorbed and contained in theabsorbent core from wetting articles which contact the absorbent articlesuch as bedsheets, pants, pajamas and undergarments. The backsheet 12may thus comprise a woven or nonwoven material, polymeric films such asthermoplastic films of polyethylene or polypropylene, and/or compositematerials such as a film-coated nonwoven material (i.e., having an innerfilm layer and an outer nonwoven layer). A suitable backsheet 12 is apolyethylene film having a thickness of from about 0.012 mm (0.5 mils)to about 0.051 mm (2.0 mils). Exemplary polyethylene films aremanufactured by Clopay Corporation of Cincinnati, Ohio, under thedesignation BR-120 and BR-121 and by Tredegar Film Products of TerreHaute, Ind., under the designation XP-39385. The backsheet 12 ispreferably embossed and/or matte-finished to provide a more clothlikeappearance. Further, the backsheet 12 may permit vapors to escape fromthe absorbent core (i.e., the backsheet is breathable) while stillpreventing exudates from passing through the backsheet. The size of thebacksheet 12 is dictated by the size of the absorbent core 18 and theexact absorbent article design selected.

The backsheet 12 and the topsheet 10 are positioned adjacent a garmentfacing surface and a wearing facing surface, respectively, of theabsorbent core. The absorbent core 18 is preferably joined with thetopsheet 10, the backsheet 12, or both in any manner as is known byattachment means such as those well known in the art. However,embodiments of the present invention are envisioned wherein portions ofthe entire absorbent core are unattached to one or both of the topsheet10 and the backsheet 12.

For example, the backsheet 12 and/or the topsheet 10 may be secured tothe absorbent core 18 or to each other by a uniform continuous layer ofadhesive, a patterned layer of adhesive, or an array of separate lines,spirals, or spots of adhesive. Adhesives which have been found to besatisfactory are manufactured by H. B. Fuller Company of St. Paul, Minn.under the designation HL-1258 or H-2031. The attachment means willpreferably comprise an open pattern network of filaments of adhesive asis disclosed in U.S. Pat. No. 4,573,986. An exemplary attachment meansof an open pattern network of filaments comprises several lines ofadhesive filaments swirled into a spiral pattern such as illustrated bythe apparatus and method shown in U.S. Pat. Nos. 3,911,173, 4,785,996and 4,842,666. Alternatively, the attachment means may comprise heatbonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds, orany other suitable attachment means or combinations of these attachmentmeans as are known in the art.

The backsheet 12 b preferably includes an inner and outer layer, each ofwhich can be bonded to the other by a variety of means known in the art,including thermal bonds, adhesive bonds, ultrasonic lamination, or thelike. Adhesive bonding can also be accomplished using adhesive slotcoating, high frequency oscillation patterns, for example in swirl orspray patterns, and other fine denier and/or high coverage applicationtechniques. Suitable laminate adhesives, which can be appliedcontinuously or intermittently, can be obtained from Findley Adhesives,Inc. or from National Starch and Chemical Company.

The outer layer (or outer cover) of the backsheet can be made in avariety of forms using different processes. For example, the outer layermay be formed as a carded web, a bonded carded web, a spunbond web, aneedled fabric, a woven fabric, or the like to provide a generallycloth-like texture to the wearer. Other additives such as titaniumdioxide can represent about 0.5% or less, particularly about 0.3% orless, of the outer layer. In one particular embodiment, the outer layercomprises a spunbond web formed of about 99.5 to 100% polypropyleneresin and about 0.5% or less other additives. The outer layer isdesirably a lightweight material having a basis weight of about 15 toabout 30 gsm and more preferably from about 15 to about 25 gsm.

The articles of the present invention additionally comprise one or moreabsorbent cores 18. The absorbent core 18 is at least partially disposedbetween the topsheet 10 and the backsheet 12 and may take on any size orshape that is compatible with the disposable absorbent article.Exemplary absorbent structures for use as the absorbent core of thepresent invention that have achieved wide acceptance and commercialsuccess are described in U.S. Pat. Nos. 4,610,678, 4,673,402, and4,888,231, and 4,834,735. The absorbent core may further comprise thedual core system containing an acquisition/distribution core ofchemically stiffened fibers positioned over an absorbent storage core asdetailed in U.S. Pat. Nos. 5,234,423 and 5,147,345.

In general, the absorbent core 18 is capable of absorbing or retainingliquids (e.g., menses, urine, and/or other body exudates). The absorbentcore 18 is preferably compressible, conformable, and non-irritating tothe wearer's skin. The absorbent core 18 may be manufactured in a widevariety of sizes and shapes (e.g., rectangular, oval, hourglass, “T”shaped, dog bone, asymmetric, etc.). The absorbent core 18 may includeany of a wide variety of liquid-absorbent materials commonly used inabsorbent articles, such as comminuted wood pulp, which is generallyreferred to as airfelt. Examples of other suitable absorbent materialsfor use in the absorbent core include creped cellulose wadding;meltblown polymers including coform; chemically stiffened, modified orcross-linked cellulosic fibers; synthetic fibers such as crimpedpolyester fibers; peat moss; tissue including tissue wraps and tissuelaminates; absorbent foams; absorbent sponges; superabsorbent polymers;absorbent gelling materials; or any equivalent material or combinationsof materials, or mixtures of these.

As discussed herein “absorbent gelling materials” and “superabsorbentpolymers” are those materials that, upon contact with aqueous fluids,such as bodily fluids, imbibes such fluids and form hydrogels. Theseabsorbent gelling materials are typically capable of absorbing largequantities of aqueous bodily fluids, and further capable of retainingsuch absorbed fluids under moderate pressures. These absorbent gellingmaterials are typically in the form of discrete, nonfibrous particles.Other forms, such as fibers, foams, sheets, strips, or othermacrostructures, are also suitable for use herein. Suitable absorbentgelling materials in the form of open cell foams may include thosedisclosed in U.S. Pat. Nos. 3,563,243, 4,554,297, 4,740,520, and5,260,345.

The configuration and construction of the absorbent core 18 may also bevaried (e.g., the absorbent core may have varying caliper zones and/orhave a profile so as to be thicker in the center; hydrophilic gradients;superabsorbent gradients; or lower average density and lower averagebasis weight zones, e.g., acquisition zones; or may comprise one or morelayers or structures). The total absorbent capacity of the absorbentcore 18 should, however, be compatible with the design loading and theintended use of the absorbent article. Further, the size and absorbentcapacity of the absorbent core may be varied to accommodate differentuses such as diapers, incontinence pads, pantiliners, regular sanitarynapkins, and overnight sanitary napkins, and to accommodate wearersranging from infants to adults. The absorbent core 18 can include otherabsorbent components that are often used in absorbent articles, forexample, a dusting layer, a wicking or acquisition layer, or a secondarytopsheet for increasing the wearer's comfort.

In certain embodiments of the present invention, the absorbent articlemay also include a sublayer disposed between the topsheet 10 and thebacksheet 12. The sublayer may be any material or structure capable ofaccepting, storing or immobilizing bodily exudates. Thus, the sublayermay include a single material or a number of materials operativelyassociated with each other. Further, the sublayer may be integral withanother element of the absorbent article or may be one or more separateelements joined directly or indirectly with one or more elements of thearticle. Further, the sublayer may include a structure that is separatefrom the core or may include or be part of at least a portion of thecore.

Suitable materials for use as the sublayer may include large cell openfoams, macro-porous compression resistant nonwoven highlofts, large sizeparticulate forms of open and closed cell foams (macro and/ormicroporous), highloft nonwovens, polyolefin, polystyrene, polyurethanefoams or particles, structures comprising a multiplicity of verticallyoriented looped strands of fibers, absorbent core structures describedabove having punched holes or depressions, and the like. One embodimentof a sublayer includes a mechanical fastening loop landing element,having an uncompressed thickness of about 1.5 millimeters available asXPL-7124 from the 3M Corporation of Minneapolis, Mn. Another embodimentincludes a 6 denier, crimped and resin-bonded nonwoven highloft having abasis weight of 110 grams per square meter and an uncompressed thicknessof 7.9 millimeters which is available from the Glit Company of Wrens,Ga. Other suitable absorbent and nonabsorbent sublayers are described inU.S. Pat. Nos. 6,680,422 and 5,941,864. Further, the sublayer, or anyportion thereof, may include or be coated with a lotion or other knownsubstances to add, enhance or change the performance or othercharacteristics of the element.

Absorbent articles suitable for use as the present invention includediapers, training pants, incontinence products, diaper pants, disposableunderwear, or the like. Suitable training pants and diaper pants canhave seamed side portions or refastenable side portions. The presentinvention is particularly suited for use with training pants or diaperpants to aid in toilet training. Particular diapers and training pantssuitable for use with the present invention are disclosed in U.S. Pat.Nos. 3,860,003, 4,636,207, 4,695,278, 4,704,115, 4,795,454, 4,900,317,4,909,803 (Reissued as USRE34920), 5,085,654, 5,492,751, 6,476,288,6,627,787, 5,507,760, 5,609,587, 5,635,191, 5,643,588, 6,118,041, SIRH1630, 5,246,433, 5,769,838, 5,899,895, 5,899,896, and 6,120,487.Additional patents discussing suitable training pants are disclosedearlier herein.

The article of the present invention may also comprise an elastic waistfeature that provides improved fit and containment; and a fasteningsystem which forms a side closure which maintains the first waist regionand the second waist region in an overlapping configuration such thatlateral tensions are maintained around the circumference of theabsorbent article to maintain the absorbent article on the wearer. Theabsorbent article may also comprise elasticized side panels (not shown)in the waist regions and to provide an elastically extensible featurethat provides a more comfortable and contouring fit and more effectiveapplication of the absorbent article. In certain embodiments, theelasticized side panels are positioned such that a front and rear sidepanel are joined to one another along their longitudinal edges. Thisjoining along the longitudinal edges of the panels may be permanent orrefastenable. For permanent joints, the panels may be adhered to oneanother via ultrasonic bonding, high tack, adhesives, etc. Forrefastenable joints, the panels may be joined via hook and loop fasters,mild co-adhesive materials, low tack adhesives, etc.

Low Basis Weight, Low Glue Burn Through Films

The films of the present invention have a basis weight of less thanabout 16 gsm, less than about 15 gsm, less than about 14 gsm, less thanabout 13 gsm, less than about 12 gsm, less than about 11 gsm, less thanabout 10 gsm, less than about 8 gsm, less than about 6 gsm.

In order to achieve low glue burn through, the films of the presentinvention may comprise polypropylene. Without being limited by theory,polypropylene usually melts at temperatures in the range of from about150° C. to about 160° C. Polyethylene, which is typically used in filmsfor absorbent articles, generally melts at temperatures in the range offrom about 100° C. to about 130° C. Films comprising both polyethyleneand polypropylene exhibit more heat resistance than polyethylene alone,thus less glue burn through occurs.

The present invention is directed to films comprising polymeric resinscomprising both polyethylene and polypropylene and/or onlypolypropylene. Such films comprise polymeric resins comprising at leastabout 10% polypropylene, at least about 20% polypropylene, at leastabout 30% polypropylene, at least about 40% polypropylene, at leastabout 50% polypropylene, at least about 60% polypropylene, at leastabout 70% polypropylene, at least about 80% polypropylene, at leastabout 90% polypropylene.

Films suitable for the present invention may be breathable films.Breathable films are polymeric films containing filler stretched tocontain internal microporosities. Breathable films are described in U.S.Pat. No. 4,472,328

Films suitable for the present invention may be coextruded. Coextrudedfilms are formed by the process of extruding two or more materialsthrough a single die with two or more orifices arranged so that theextrudates merge and weld together into a laminar structure beforechilling. Each material is fed to the die from a separate extruder, butthe orifices may be arranged so that each extruder supplies two or moreplies of the same material. Coextrusion can be employed in film blowing,free film extrusion, and extrusion coating processes. The advantage ofcoextrusion is that each ply of the laminate imparts a desiredcharacteristic property, such as stiffness, heat-sealability,impermeability or resistance to some environment, all of whichproperties would be impossible to attain with any single material.

According to the present invention, a model was created to predict glueburn through using heat transfer principles. This model for determiningglue burn through involves measuring the thermal conductivity andthermal effusivity of the film. Thermal conductivity is a physicalproperty that characterizes a substance's ability to transfer heat. Thethermal conductivity differs with each substance's structure, density,humidity, pressure, and temperature. Materials having a large thermalconductivity value are good conductors of heat and those with smallvalues are good insulators. Thermal effusivity is the property thatdictates the interfacial temperature when two semi-infinite objects atdifferent temperatures touch one another. After incorporating thethermal properties into the model, a predictive glue burn through valueis achieved reflecting present conditions of the film.

The ratio below describes the ability of the polymer barrier film toresist glue burn through. In this model, glue burn through is correlatedto heat capacity×density.GBT=Cpρ=(effusivity)²/κ

Wherein: Cp=heat capacity, J/kg-Kelvin

-   -   κ=Thermal Conductivity, watt/meter-Kelvin    -   ρ=density, g/cc or kg/cubic meter    -   Thermal Effusivity units are watt-second^(0.5)/meter²-Kelvin

The model predicts that a heat capacity×density value of greater thanabout 970,000 Ws/m³K, greater than about 1,000,000 Ws/m³K, greater thanabout 1,050,000 Ws/m³K, 1,100,000 Ws/m³K, 1,200,000 Ws/m³K is indicativeof a film having low glue burn through. The model predicts that a heatcapacity×density value of less than about 970,000 Ws/m³K shows visibleglue burn through. Calculating the glue burn through is accomplished bymeasuring the thermal effusivity and thermal conductivity of the polymerbarrier film.

Thermal Conductivity and Thermal Effusivity Test Method

Thermal conductivity and thermal effusivity measurements for solidmaterials may be obtained by sending samples to Mathis Instruments at 21Alison Blvd. in Fredericton, N.E. There, a Mathis TC-01™ ThermalConductivity Analyzer is used to make the calculations. The method isknown as the Modified Hot Wire technique. This method requires a numberof 7.62 centimeter square plies such that at least 1 millimeter ofthickness under a weight of 652 grams over an area of 250 squaremillimeters will be achieved. The material used for the sample should beequilibrated for at least 2 hours at a temperature of 23 degrees C.(+/−2 degree C.) and 50% (+/−2%) relative humidity. The machinedirection of each ply should be noted and all should be placed in thesame orientation, such orientation should be parallel with the axis ofthe longer dimension of the machine's sensor. The method employed is tobe consistent with the principles of operation for the Mathis TC-01.

In the case of testing a polymer barrier film that is contained in anarticle, the film must be removed from the article and the film'ssurfaces cleaned of any contaminating materials such as glue, fiber,etc. It is helpful if the entire sheet of barrier film is removed froman article so that the contaminants can be removed with as little damageas possible to the film. The pieces of film can then be marked fororientation and cut to uniform size approximately at least 10centimeters square. These pieces can then be gently treated with asolvent that will dissolve the hot melt adhesives while not causingdamage or swelling to the film. Suitable solvents include, but are notlimited to methylene chloride or acetone. The available plies of filmshould then be carefully stacked on top of each other with all piecesoriented in the same direction. The stack of plies should then beconditioned and rolled with a hard rubber or steel roller of similarwidth to that of the plies weighing 2 kg to 4 kg to press out the excessair or pockets of air between the plies. The sample, if it meets theabove thickness requirement and is then cut to 7.62 centimeters on eachside, is then ready to be tested.

The test procedures conducted at Mathis Instruments includes thefollowing steps:

-   -   Place a 652 g weight on the top of the at least 1 mm thick        sample to optimize sample contact with the spring-loaded sensor.    -   Permit the sample sufficient time to stabilize to iso-thermal        conditions with the environment and sensor.    -   Place the sample and sensor inside an environmental chamber for        testing at elevated temperature.    -   Set up the instrument using the following parameters: a        10-second test time, 4-second start time and 5-minute cooling        interval.    -   For each sample received, three thermal conductivity        measurements are performed at 50° C. using the auto test mode.    -   For each sample received, three thermal effusivity measurements        are performed at 50° C. using the auto test mode.    -   Report the average of the 3 readings for each property.

The thermal conductivity and thermal effusivity measurements are thenincluded in the aforementioned equation to predict the glue burn throughvalue via the heat capacity×density equation.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An absorbent article comprising: a liquidpervious topsheet; a backsheet at least partially joined to thetopsheet; an absorbent core disposed at least partially between thetopsheet and the backsheet; a leg cuff extending along a longitudinaledge of the topsheet; wherein the backsheet comprises a polymeric filmhaving a heat capacity×density value of greater than about 970,000Ws/m³K as measured in the method described herein, the film having abasis weight of less than about 8 gsm, the film comprising a polymericresin that comprises at least about 10% of polypropylene.
 2. Theabsorbent article of claim 1, wherein the polymeric film has a basisweight is less than about 6 gsm.
 3. The absorbent article of claim 1,wherein the polymeric resin comprises at least about 20% ofpolypropylene.
 4. The absorbent article of claim 1, wherein thepolymeric resin comprises at least about 30% of polypropylene.
 5. Theabsorbent article of claim 1, wherein the polymeric resin comprises atleast about 50% of polypropylene.
 6. The absorbent article of claim 1,wherein the polymeric resin comprises at least about 70% ofpolypropylene.
 7. The absorbent article of claim 1, wherein thepolymeric resin comprises at least about 90% of polypropylene.
 8. Theabsorbent article of claim 1, wherein the absorbent article is a diaper.9. The absorbent article of claim 1, wherein the polymeric film is abreathable film.